Cord tension control for top down/bottom up covering for architectural openings

Abstract

Cord tensioning systems are provided for top down/bottom up coverings to prevent entanglement of lift cords about associated wrap spools by correlating rotation of the wrap spools with translating threaded nuts mounted on threaded shafts rotating in unison with the wrap spools whereby abutment of nuts associated with lift spools prevent over movement of rails associated with the spools and thus entanglement of the lift cords associated therewith.

What is claimed is: 
     
       1. A top down/bottom up covering for an architectural opening comprising in combination:
 a headrail; 
 at least two horizontally disposed vertically movable rails supporting at least one panel of collapsible shade material; 
 at least two flexible lift cords affixed to each rail; 
 a control system component associated with each rail, each component including an elongated drive shaft, a system for reciprocally and reversibly rotating said drive shaft about its longitudinal axis, a wrap spool rotatable with said drive shaft and connected to a lift cord such that said lift cord can be wrapped about or unwrapped from said wrap spool, vertical movement of said rails being effected by wrapping and unwrapping of said lift cords about said spools, and a cord tension control system for preventing said lift cords from becoming entangled at said wrap spools, said cord tension control system including a threaded shaft associated with and rotatable in unison with each drive shaft, a nut threaded on each of said threaded shafts for translating movement along an associated shaft, the nuts on said threaded shafts overlapping in their path of travel along an associated threaded shaft whereby upon engagement of said nuts with an adjacent nut the drive shafts will be prohibited from rotating in a predetermined direction thereby prohibiting the wrap spools on said drive shafts from rotating; 
 said cord tension control system further including a housing in which said threaded shafts are rotatably mounted, fixed abutments in said housing in engagement with said threaded shafts to prevent a predetermined amount of axial movement of said shafts in a predetermined direction and resilient members in said housing biasing each of said shafts against said fixed abutments. 
 
     
     
       2. The covering of  claim 1  wherein said resilient members are springs fixedly mounted relative to said housing and engaging an associated threaded shaft. 
     
     
       3. The covering of  claim 2  wherein said threaded shafts include protrusions for engagement with said fixed abutments. 
     
     
       4. The covering of  claim 3  wherein said protrusions are axially spaced radially extending rings. 
     
     
       5. The covering of  claim 1  wherein said housing has side walls and a bottom wall, said springs being mounted on said side walls. 
     
     
       6. The covering of  claim 1  wherein said housing has side walls and a bottom wall, said springs being mounted on said bottom wall. 
     
     
       7. The covering of  claim 1  wherein said housing has side walls and a bottom wall and said fixed abutments are on said bottom wall. 
     
     
       8. The covering of  claim 4  wherein there are at least two of said rings. 
     
     
       9. The covering of  claim 8  wherein there are three of said rings. 
     
     
       10. The covering of  claim 1  wherein at least one of said fixed abutments is positioned between two of said rings. 
     
     
       11. The covering of  claim 4  wherein at least one of said rings includes a radial tooth for engagement with a fixed abutment to prevent rotation of the threaded shaft. 
     
     
       12. The covering of  claim 4  wherein at least one of said rings includes a radial tooth for engagement with the nut on the associated threaded shaft. 
     
     
       13. A covering for an architectural opening comprising:
 a headrail; 
 at least two rails supporting at least one panel of shade material; 
 at least two flexible lift cords affixed to each rail; 
 a control system component associated with each rail, each component including a drive shaft, a system for rotating said drive shaft about its longitudinal axis, a wrap spool rotatable with said drive shaft and associated with a lift cord so that said lift cord can be wrapped about or unwrapped from said wrap spool, vertical movement of said rails being effected by wrapping and unwrapping of said lift cords about said wrap spools, and 
 a cord tension control system including a threaded shaft rotatable in unison with each drive shaft, a nut threaded on each of said threaded shafts for movement along an associated threaded shaft, said nuts on said threaded shafts overlapping in their path of travel along an associated threaded shaft so that rotation of said drive shafts is restricted upon engagement of one of said nuts with another of said nuts, thereby restricting rotation of said wrap spools on said drive shafts; 
 said cord tension control system further including a housing in which said threaded shafts are rotatably mounted, fixed abutments in said housing in engagement with said threaded shafts to restrict axial movement of said shafts, and resilient members in said housing biasing each of said shafts against said fixed abutments. 
 
     
     
       14. The covering of  claim 13  wherein said resilient members are springs fixedly mounted relative to said housing and engaging an associated threaded shaft. 
     
     
       15. The covering of  claim 14  wherein said threaded shafts include protrusions for engagement with said fixed abutments. 
     
     
       16. The covering of  claim 15  wherein said protrusions comprise at least two axially-spaced, radially-extending rings. 
     
     
       17. The covering of  claim 16  wherein at least one of said fixed abutments is positioned between two of said rings. 
     
     
       18. The covering of  claim 13  wherein said housing has side walls and a bottom wall, said springs being mounted on said side walls. 
     
     
       19. The covering of  claim 13  wherein said housing has side walls and a bottom wall, said springs being mounted on said bottom wall. 
     
     
       20. The covering of  claim 13  wherein said housing has side walls and a bottom wall, and said fixed abutments are on said bottom wall.